I developed an interest in the complexities of cell biology and immunology during my undergraduate studies at Drexel University, which I continued to foster after my undergraduate studies, where I worked at the University of Pennsylvania in the Department of Infectious Diseases in Medicine engineering and characterized various novel Vaccinia virus vectors to be used as live vaccine prophylactics. I then went on to graduate school at Thomas Jefferson University where I broadened my studies to include general cell biology, developmental biology and immunology studying in vivo and in vitro immune responses to Hepatits B virus. During my post doctoral studies, I have been able to further characterize the lymphopoietic defects in the collagen X transgenic and null mice, as well as describe the immune response defects at both a cellular level in vitro and in vivo with parasite challenges. The outcome of my postdoctoral work is a proposed model depicting the hematopoietic niche in the cartilage-bone junction, which I will test further in this K01 award. This proposal will be a continuation of my post doctoral work characterizing the link between endochondral ossification (EO), where hypertrophic cartilage is replaced by bone and marrow, and the establishment of a hematopoietic niche. To do this, collagen X transgenic and null, perlecan hypomorphic and syndecan-1 null mice will be used, since we propose that, as in collagen X mice, the disease phenotypes of all these mice may involve growth plate defects, an altered marrow environment and aberrant hematopoiesis. We proposed that collagen X and heparan sulfate proteoglycans, e.g. perlecan and syndecan-1, provides a structural network that sequesters cytokines in hypertrophic cartilage, and network disruption may cause inappropriate signaling at the chondro-osseous junction (COJ) leading to defective hematopoiesis. To test this, 1) bone marrow transplants, co-cultures and cytokine analyses will confirm the altered marrow environment and identify the COJ resident cell type (stomal, hypertrophic chondrocyte, or osteoblast) unable to support hematopoiesis in the collagen X mouse, 2) ectopic bone forming assays will confirm EO generates the hematopoietic niche and that collagen X mice are defective in this process, and 3) flow cytometry and co-culture assays will confirm and begin to characterize the hematopoietic defects in the perlecan hypomorphic and syndecan-1 null mice. These data are an extension to the completed aims of a NRSA awarded to this investigator, and will provide data towards future goals of characterizing the extracellular matrix contribution to cytokine rich niches in development and disease. These studies will be performed at the University of Pennsylvania, which is ranked among America's top recipients of competitive research grants, earning more than $500 million in external funding annually. The specific research environment that I will be working is in the Department of Animal Biology at the School of Veterinary Medicine. The members are an exclusively basic science group, consisting of ~20 standing (Assistant to Full) professors, and 7 research professors, all of who are funded by NIH or NSF, and are conducting active research in biochemistry, cell, molecular, and developmental biology. Subjects under investigation include skeletogenesis, hematopoiesis, transgenesis and spermatogonial transplanation, cloning, mitochondria, pattern formation, chromatin structure, angiogenesis, arginylation as a posttranslational modification, transcriptional regulation of differentiation, growth hormones, respiration, cell cycle, cell death, spermatogenesis, obesity, stress, immunology, eye development, and dinosaur paleobiology. The faculty and postdoctoral fellows interact at department seminars, and there is good exchange of ideas, technical assistance, and sharing of facilities. Opportunities for interactions outside of the Veterinary School are effortless, since we are within the University of Pennsylvania campus, which includes the Medical and Dental Schools, Wistar Institute, as well as Children's Hospital of Philadelphia. Further, at the University of Pennsylvania we have the opportunity to participate in may intercollegiate seminars and symposiums with Thomas Jefferson University, Fox Chase, Temple University, and the many small collages in the surrounding suburbs of Philadelphia. Finally, the Penn faculty members that will provide me with a unique opportunity to seek advise in skeletal/matrix biology, hematology, and B cell biology, including: Drs. Jacenko and Emerson (my mentors), Drs. Hankenson, Soslowsky, and Adams (on my mentoring committee), Drs. Cancro and Akintoe (my collaborators), and the numerous faculty members that I will interact with at the many journal club, seminar, and symposiums offered at Penn and the surrounding schools.